EDITORIAL NEWSLETTER WINTER 2009/2010. Dear colleague,

Transcription

1 EDITORIAL NEWSLETTER WINTER 2009/2010 Dear colleague, Contents Welcome to our third newsletter. Please forward to your colleagues to encourage their participation in the X3-Noise Network and to draw attention to the website on which we can and do provide topical information. The most recent news, concerning the TIMPAN project which has been completed, and the newly started VALIANT project, are available on the website. Information of all ongoing projects is updated regularly, as well as the Research Organisations' annual reports, Calendar and News sections. Best regards, Dominique Collin X3 Noise Coordinator Stephen Chow X3-Noise WP4L Communications & Feedback Editorial Open rotor noise: back in the spotlights Projects Corner Past and Forthcoming Events More capabilities for you on the Website Page 1 sur 7

2 Open rotor noise back in the spotlights Because of the growing concern on CO2 emissions, and because of the expectation that fuel prices will increase considerably in the long term, the aircraft industry is diligently searching for high efficiency propulsion systems for the next generation short-tomedium haul aircraft. A propulsion system that offers the prospect of being much more efficient than todays turbofan engines, is the contra-rotating open rotor (or contra-rotating propeller), abbreviated as CROR. Preliminary estimates amount to a reduction in fuel consumption of 20 to 25%. Such powerplants have previously been the focus of a large research undertaking led by NASA and US industry in the late 1970s and 1980s, motivated by the high fuel costs arising from the 1973 oil crisis. Significant advances in the development of engines were achieved, but primarily due to the decrease in oil prices, interest in bringing these engines to market waned. In today s context of increased focus on fuel efficiency and environmental impact, the primary challenges for the realization of such a commercially viable engine relate to the issues of noise emissions and installation effects with the airframe. Noise emission is different from that of a turbofan engine, as the rotor is not shielded from the ambient air by a nacelle. This may be an obstacle to achieve the aviation industry s equally challenging targets on noise reduction. Therefore, research has been initiated to assess the noise generation by contra-rotating propellers, e.g. in the EU-funded project DREAM (validation of Radical Engine Architecture systems), which had its kick-off in February Results from this and other relevant projects have not been published yet, but some papers on state-of-the-art computational methods have already appeared, such as the paper Low-Speed Aerodynamics and Aeroacoustics of CROR Propulsion Systems, by A. Stuermer and J. Yin of DLR, presented at the 15th AIAA/CEAS Aeroacoustics Conference, May 2009, in Miami, Florida. In this paper, a CFD and an aeroacoustic analysis tool have been employed for the analysis of the complex aerodynamics and aeroacoustics of this type of propulsion system. In order to demonstrate the codes applicability to these types of simulations as well as to develop an understanding of the impact of configuration variations, a generic 8x8 and 10x8 pusher CROR powerplant are studied here at typical sea-level take-off conditions of M = 0.2. The results allow for a detailed analysis of the aerodynamic interactions between the two rotors as well as the noise generation mechanisms, allowing for an improved understanding of interaction tone sources. Reference: Arne Stuermer and and Jianping Yin, Low-Speed Aerodynamics and Aeroacoustics of CROR, AIAA Paper Page 2 sur 7

3 Projects Corner EU Project TIMPAN concluded TIMPAN (Technology to Improve Airframe Noise) was a 3-year project of the European Community 6th Framework Programme, Priority Aeronautics and Space, launched in 2006, addressing the community noise reduction objectives for commercial aircraft by focusing on the airframe noise issue, caused by turbulent flow around the landing gear and the high-lift wing and responsible for about half of the total noise in approach situation for aircraft of recent design. The final meeting was held on Nov in Toulouse. A workshop was organised in complement to the official project closure review and focussed on most relevant technologies studied within TIMPAN. In particular, ways to further improve these technologies had been discussed. TIMPAN brought together 14 actors from the European aeronautics industry including aircraft manufacturers (Airbus and Dassault Aviation), landing gear manufacturers (Messier-Dowty and Messier Bugatti), key research institutes (DLR, ONERA, NLR, EADS-IW), universities (University of Southampton, Technical University of Braunschweig) and SMEs (ATECA, Free Field Technologies). TIMPAN addressed both sources (landinggear and high-lift) through investigation of innovative technologies and improvement of advanced low-noise designs. Mid-term objective is a 5 db airframe noise reduction with respect to 2000 state-of-the-art. Participants of the TIMPAN final meeting Achievements on landing-gear: Plasma actuators and air curtain technologies, providing each a broadband noise reduction of 3 to 5 db on component, have proved to be relevant breakthrough technologies for long-term implementation. However, these innovative technologies will not be available to meet the mid-term challenge of 5 db on airframe noise as further developments are needed for assessing their potential on representative aircraft components and for solving related integration issues. Main outcomes result therefore from the improvement of advanced low-design on the main-landing gear. In the EU-Project SILENCER advanced low noise gears had been investigated [1]. In the EU- Project TIMPAN still more advanced concepts were developed and noise tested on a ¼ scaled main landing gear model in the 6 m by 6 m open test section of DNW-LLF (German-Dutch Wind Tunnel Large Low Speed Facility). The model test results were transposed to full scale and compared against the full scale SILENCER A340 style main landing gear test results. In TIMPAN different modifications of the major gear components in combination with flow transparent fairings and variations of both bogie inclination and wheel spacing were tested. An optimal combination of all tested gear modifications led to a noise reduction of up to 8 db(a) in terms of overall A-weighted noise levels, relative to the SILENCER reference gear configuration (Fig. 1) which corresponds to more than 6 db landing-gear noise reduction in approach. The main Page 3 sur 7

4 contributions to this noise reduction originates from an increase in toe down bogie inclination angle, both a flow transparent bogie and torque link fairing, a low noise side-stay, brake and legdoor design in combination with a ramp. Figure 1 Comparison of non-dimensional 1/3-oct. band noise spectra for the SILENCER reference and the TIMPAN low noise configuration for an aircraft overhead position [1] Dobrzynski, W., Schöning, B., Chow, L. C., Wood, Ch., Smith, M., Seror, Ch.: Design and Testing of Low Noise Landing Gears, AIAA/CEAS , 11th AIAA/CEAS Aeroacoustics Conference, Monterey / USA, May, Achievements on high-lift devices: Slotted slats constitute the major noise sources of today s high-lift systems of large commercial aircraft. In TIMPAN, three approaches are considered. The first one consists in developing a slatless concept supported by a wing-flap flow arrangement (Coanda effect). The second approach is linked to the implementation of add-on treatments (wing leading edge liner, slat wire meshes, slat trailing edge treatments) and the third one to the slat setting (slat gap and overlap) optimization. The slat-less concept is surely the most aggressive technology. While allowing maintaining required aircraft performance and reducing strongly airfoil noise, it leads to severe integration issues as important air-flow shall be supplied. Add-on treatments may provide good source noise reduction but generally lead to performance degradation and in turn poor results. Most relevant outcome is therefore the slat setting optimization, which proved that a compromise in term of low-speed performance may be found for optimizing airframe noise in approach. With respect to the reference setting a noise reduction of up to 3.5 db on airfoil noise has been demonstrated. 10 db SR, U_test=50m/s, U_flight=75m/s, AoA = 6 OverLap: -1.5 mm SPL (db) Frequency (Hz) Gap: 3 mm Gap: 7 mm Gap: 4.9 m m Figure 2 Slat gap reduction impact on airfoil noise measured on a 2d profile at 50m/s and 6 of angle-of-attack Page 4 sur 7

5 EU Project VALIANT Kick-off On 28 and 29 September 2009 the kick-off meeting of the EU project VALIANT (VALidation and Improvement of Airframe Noise prediction Tools) was held, at the Von Karman Institute in Brussels. VALIANT is an upstream research-oriented project, which tackles the problem of broadband turbulent noise sources. Broadband noise generated by the turbulent flow around the airframe is one of the most important components of aircraft generated acoustic nuisances and its prediction and subsequent reduction is essential for achieving the ACARE 2020 objectives of noise level reductions. The complexity and diversity of broadband turbulent noise sources makes that prediction extremely challenging. This challenge is tackled by generating new experimental data and improving and validating numerical tools for prediction of airframe noise (AFN) generated from landing gears, slats, flaps and local separation regions. The extremely complex physical nature of the phenomenon and the high computational cost of computing full aircraft configurations, on one hand, and a lack of a reliable experimental database, on the other hand, require focusing the evaluation of the existing approaches and their further improvement on key generic test cases representing major broadband AFN mechanisms, associated with multiple body interactions: two-struts (landing gear), wing-flap, slat-wing and gap-turbulence. For all these configurations, the links between the noise prediction chain are addressed (turbulent/source region, near- and far-field propagation domains) and avenues of improvements are analyzed and developed. It is expected that by validating and improving the predictive tools, which is the main objective of the VALIANT project, a deeper insight into the mechanisms behind AFN will be obtained, which is an essential step towards new efficient AFN reduction concepts and their optimization to achieve the required breakthrough towards quieter aircraft. The consortium is formed by European and Russian partners, who intend to collaborate in a strong interaction, relying on the complementary expertise of each partner. The consortium is formed by 2 universities, 7 research establishments, 2 SME s and 1 industry, all with recognized expertise in aeroacoustics. Participants of VALIANT Kick-off meeting. Page 5 sur 7

6 Past Events Papers and presentations on aeroacoustics and noise control of flight vehicles presented on the Inter-Noise 2009 in Ottawa Papers presented and discussed during the Inter-noise 2009 congress can be divided into the following areas, which roughly correspond to the congress sessions: Significant contribution was on Aircraft and Airport Noise Control with 47 papers presented in several sessions: The most important sessions focused on these topics were Aircraft Interior Noise (14 papers), Airport Noise (15 papers) and the Effects of Noise on Communities and Community Noise sessions (11 papers). The sizeable number of the presentation from the community noise reflects the increasing interest in this field. The wide range of research presented in these sessions put forward an exceptional level of theoretical and experimental knowledge necessary for designing quieter aircraft. Of particular interest are several studies concerning the application of smart materials and active noise control for noise control of airplanes and helicopters. The other papers concerning aeroacoustics were presented in the Aeroacoustics and Fan Noise sessions. A total of 6 papers, including theoretical and experimental studies of jet noise, fan noise, and active noise control in ducts were presented. Traditionally the main interest deals with computational techniques used for modeling and prediction of turbulent flow, nevertheless some papers were also focused on aeroacoustics measurement techniques. One particularly vital contribution of this international meeting is the amount of knowledge exchange between specialists from many areas (aeroacoustics, noise control, psychoacoustics, etc.) who share a common interest, namely the reduction of aircraft noise X3-Noise Full Network Meeting and Workshop Resolving uncertainties in airframe noise testing and CAA code validation The 4th Scientific Workshop of X3-NOISE, also named the 13th CEAS-ASC Workshop, was held in the Palace of Parliament in Bucharest, Romania, on October 1-2, Its title was: Resolving uncertainties in airframe noise testing and CAA code validation. The workshop had three keynote speakers and four sessions, for details see: The meeting was closed by a final discussion on the main issues and prospects resulting of the presentations. You can find programme the proceedings on the Public website! Page 6 sur 7

7 Forthcoming Events 2009 X3-Noise Seminar Noise Mapping The X3-Noise Seminar on Noise Mapping (of Aircraft Noise) has been moved to probably in April The major objectives are: - Evaluate 2007 END noise mapping exercise - Provide recommendations for 2012 exercise - Maintain consistency with international developments It is expected that this seminar will attract a range of stakeholders including those from: the Aviation Industry, Noise Mappers and from Related Networks. Early expressions of interest to local organiser: Anotec - Nico van Oosten contact form ( More Capabilities for you on the Website Public showcase The main X3-Noise Website, is an easy-to-use public showcase of the aircraft noise work in Europe - providing summary information on EU-supported aircraft noise Projects and contact information to national and regional focal points. We hope that you find particularly helpful (and contribute to) the frequent News items ( and the Environmental Calendar ( giving advance notice of our own and closely related Events - Workshops/Seminars/Conferences. A newly introduced feature is the page on which aeroacoustics Research Organisations Annual Reports ( are published. See and use the new features and/or contact us ( Stephen Chow WP4 Leader Communications & Feedback Paola Nebuloni, Website Content Manager Rinze Krol, Website Design & Realisation Secure showcase A new secure website is now working on All the files on the old Secure Website have been moved to the new Secure Website, but please check if you can find your deliverables! You should have received an invitation to login on If you have, please follow the instruction. You have one month to respond to the invitation. After this period, your login will be cancelled. See and use the new features and/or contact us ( Stephen Chow WP4 Leader Communications & Feedback Paola Nebuloni, Website Content Manager Rinze Krol, Website Design & Realisation Page 7 sur 7